Curvature from surface

Hello everyone!

I need to evaluate the curvature of a surface. My problem is the following:

1. I have a semisphere (x,y,z where z is the elevation and (0,0,0) is located on the inner center of the semisphere), with some irregularities over the survace.

2. I would like to evaluate the radius of curvature of each point on the surface. I want to restrict the curvature to the plane curvature. That is, if i choose a point, I choose the plane which contains the point and the zero, and is parallel to the z axis. This plane draws a profile of the deformed sphere's surface. I want to evaluate the radius of curvature in this plane.

3. I have seen similar formulations, but they give me the curvature associated to the surface, which I don't need. These formulations include the definition of a weak form PDE.

Could you help me? I have few experience with Comsol

Thanks in advance!!